Q: Which equation should be used to calculate the probability of an offspring's genotype when one parent has two possible genotypes?

$$\text{Prob(offspring)} = \text{Prob(parent has genotype 1)} \times \text{Prob(offspring | parent has genotype 1)} + \text{Prob(parent has genotype 2)} \times \text{Prob(offspring | parent has genotype 2)}$$

Question 1

Which genetic phenomenon is illustrated by the variety of squash colors in the first image?

Accepted Answer

Pleiotropy

Question 2

In the Drosophila cross shown in the third image, what is the expected phenotypic ratio of red-eyed to white-eyed offspring in the F2 generation?

Accepted Answer

$$1:1$$

Question 3

Which of the following best explains why female mammals are genetic mosaics for X-linked traits, as shown in the sixth image?

Accepted Answer

Random inactivation of one X chromosome in each cell during early development

Question 4

A woman is heterozygous for an X-linked gene. What is the expected pattern of expression in her tissues?

Accepted Answer

Mosaic expression due to random X inactivation

Question 5

A nonsense mutation at the second codon of a gene results in a protein that is only two amino acids long. Which term best describes this allele?

Accepted Answer

Null/amorphic

Question 6

Which of the following is an example of a gain-of-function mutation?

Accepted Answer

A mutation that causes a protein to be expressed in tissues where it is normally not expressed

Question 7

In a cross between a man with blood type A (whose mother was type O) and a woman with blood type AB, what is the probability that their child will have blood type A?

Accepted Answer

$$\frac{1}{2}$$

Question 8

Which of the following best describes incomplete dominance?

Accepted Answer

The heterozygote has a phenotype intermediate between the two homozygotes

Question 9

A pedigree shows unaffected parents with an affected child. What mode of inheritance is most likely?

Accepted Answer

Autosomal recessive

Question 10

Which of the following is a feature of X-linked recessive inheritance?

Accepted Answer

Trait is only seen in homozygous females and hemizygous males

Question 11

What is the effect of X chromosome inactivation in female mammals?

Accepted Answer

One X chromosome is randomly inactivated in each cell, leading to mosaicism

Question 12

Which of the following best describes pleiotropy?

Accepted Answer

One gene affects multiple phenotypic traits

Question 13

A child is born with PKU, an autosomal recessive disorder. If both parents are carriers, what is the probability that their next child will also have PKU?

Accepted Answer

$$\frac{1}{4}$$

Question 14

Which of the following is an example of co-dominance?

Accepted Answer

A person with blood type AB expressing both A and B antigens

Question 15

Which equation should be used to calculate the probability of an offspring's genotype when one parent has two possible genotypes?

Accepted Answer

$$	ext{Prob(offspring)} = 	ext{Prob(parent has genotype 1)} 	imes 	ext{Prob(offspring | parent has genotype 1)} + 	ext{Prob(parent has genotype 2)} 	imes 	ext{Prob(offspring | parent has genotype 2)}$$

Question 16

Which of the following is an example of a hypomorphic mutation?

Accepted Answer

A mutation that results in reduced but not absent protein function

Question 17

Which of the following best describes the concept of penetrance?

Accepted Answer

The proportion of individuals with a particular genotype that actually display the associated phenotype

Question 18

Which of the following is a real-world example of gene-environment interaction?

Accepted Answer

PKU patients developing intellectual disability only if exposed to phenylalanine in their diet

Question 19

Which of the following is true about X-linked dominant inheritance?

Accepted Answer

Both males and females can be affected, and the trait is seen in every generation

Question 20

Which of the following best describes epistasis?

Accepted Answer

A gene at one locus alters the phenotypic expression of a gene at a second locus

Gene Interactions and Variations from Classic Mendelian Genetics

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